1. Field of the Invention
The present invention relates to a liquid ejection apparatus and, more specifically, to a liquid ejection apparatus for applying the liquid which ejects from nozzle openings of a nozzle plate mounted on a liquid ejection head.
2. Related Art
Conventionally, when a liquid is applied all over the margin of a recording medium such as papers, the liquid is ejected over the region larger than the size of the recording medium because the recording medium and the liquid ejection head may be displaced. Therefore, the liquid is also ejected to the region around both side edges and the top and bottom edges of the recording medium where the recording medium is not disposed. If the liquid which has not been applied to the recording medium is left, the liquid ejection apparatus itself, an undesired region of the recording medium and the hands of the user may be smeared.
Additionally, each liquid droplet ejecting from the liquid ejection apparatus is extremely small in volume up to several pl or pico-litter in order to improve the resolution of recording. Since the mass of such micro droplets is extremely small, the kinetic energy is rapidly lost due to the viscosity resistance of atmosphere as soon as those eject out in the air. For example, when the droplet of which amount is less than 8 pl travels in air by around 3 mm, the velocity becomes approximately zero. Meanwhile, the distance obtained by adding the interval between the recording medium and the absorbing member, and the gap between the nozzle plate and the recording medium is around 3-5 mm. Therefore, a part of the droplets which has not been applied on the recording medium loses the kinetic energy before arriving at the absorbing material. As for the droplets without the kinetic energy, the falling motion due to the acceleration of gravity and the viscosity resistance of atmosphere are approximately proportional, so that it takes a long time to completely fall the droplets.
Here, if the ejection velocity is increased in order to extend the travel distance of droplets, the viscosity resistance in atmosphere which acts on the droplet is further increased, so that the travel distance is shortened despite the intention. Additionally, if the ejection velocity is increased, the remarkably micro droplets referred to as a satellite ink, which are generated when the droplets are released from the nozzle plate is easily generated, undesirably.
Further, an operation referred to as a flushing is periodically performed in the liquid ejection apparatus. The flushing is an operation that the liquid ejection head without any recording medium is operated and the liquid is ejected. Thereby the liquid with the increased viscosity in the nozzle which is not frequently used is removed. However, the liquid ejected in the flushing is consumed only for the flushing and does not contribute to record the recording medium. Accordingly, small or fine liquid droplets eject in order to reduce the consumption of the liquid. Additionally, since the time required for the flushing causes the throughput of a recording operation to decrease, the liquid ejects from all the nozzles within a short time when the flushing is performed. In such flushing operation, the large amount of satellite ink is generated.
Most satellite ink generated under the above described various conditions floats around the region in which the liquid ejection head is moved and becomes aerosols. A part of the aerosols floats up to the outside of the liquid ejection apparatus and deposits around the liquid ejection apparatus. Then, most of the aerosols deposit on each section in the liquid ejection apparatus. Here, when the aerosols deposit on a convey path of the recording medium, such as a platen, the recording medium which is subsequently conveyed is polluted. Additionally, when the aerosols are deposited on an electric circuit, a linear scale or various optical sensors in the liquid ejection apparatus, it may cause the malfunction of the apparatus in itself. Further, when the user touches the sections on which the aerosols are deposited, the hands of the user are polluted. Thus, a technology for collecting the liquid which has not been applied on the recording medium has been proposed as disclosed, for example, in Japanese Patent Application Publication No. 11-320891.
Here, a mechanism is proposed, for guiding the liquid which travels to and arrives at a platen without applying on the recording medium into an waste liquid container different from the platen in a liquid ejection apparatus. In the liquid ejection apparatus, a through-hole is provided in the platen, and the liquid in the platen is guided into the individual waste liquid container via the through-hole. Therefore, it is prevented that the large amount of liquid remains in the platen and that any airborne droplet or mist is generated due to bumping the droplets against each other.
However, since the amount of liquid applied on the platen is not constant, it unexpectedly takes time to discharge the liquid to the outside of the platen, so that the liquid may sometimes remain oh the platen. In this case, it is impossible to prevent mists from generating. Additionally, if the discharge of liquid on the platen is delayed, the medium of liquid is evaporated and a nonvolatile component remains on the platen. When the nonvolatile component is accumulated on the platen, the recording medium which is in contact with the platen is polluted, and the irregularity of the surface of the fluid channel is generated on, the platen. Therefore, the flow of the waste liquid may be easily stopped.
To solve the above-described problems, a liquid ejection apparatus including an absorbing means is proposed in Japanese Patent Application Publication No. 2004-202867. The liquid ejection apparatus includes the absorbing means made of a porous material on the platen, for receiving the liquid which has not been applied on a recording medium and absorbing the same. The absorbing material has suction power in itself due to capillarity, so that the received liquid is held therein without scattering outside.
Additionally, another liquid ejection apparatus has been proposed in Japanese Patent Application Publication No. 2004-202867. In the liquid ejection apparatus, a metal member which will be an electrode is disposed on the surface of the, absorbing means, and an electric field is formed between a metal nozzle plate for ejecting liquid and the electrode. Since droplets ejecting from the nozzle plate are charged with the pole same as that of the nozzle plate, the droplets travel toward the electrode without decreasing the velocity due to coulomb force acting between the electric field and itself, and then are adsorbed on the electrode. The droplets adsorbed on the electrode are finally absorbed in the absorbing member.
As described above, the absorbing member made of the porous material has been used in the liquid ejection apparatus in order to absorb the liquid which arrives at the platen without applying on the recording medium. Here, since the absorbing member using the porous material has a function for holding liquid due to the capillarity in itself, a certain amount of liquid is continually held therein. However, the volatile component of the held liquid is evaporated around the surface of the absorbing member, so that the nonvolatile component is intensively accumulated adjacent to the surface of the absorbing member. Therefore, the absorbing member is clogged so that the desired function of the absorbing member, which receives the liquid without generating any mist may be lost. Additionally, most nonvolatile component accumulated on the surface of the absorbing member includes pigment composition. Thereby the recording medium subsequently provided may be polluted.